SOS ECU Tune questions about who has had this installed and their experiences.....

I have been going back and forth whether or not to get the RDX injectors and Prospeed tune spec 2/ or the just the stage 2 Prospeed ecu rom tune with the stock injectors??

I called SOS out of curiosity to see if they offered a ecu rom tune for my 91 and they said that they use to have them but stop selling them a couple of years ago because people were leaning more towards stand alone units to tune their cars. He said that they still have some chips/tune in stock and they would sell me one for $100! All I would need to do is have a local shop solder the chip onto my ecu. I've never heard of anybody mentioning a tune from SOS, so I thought I would get a feeler out their to see if anyone had any experience with this particular tune?? They said that I should expect between 9-10 hp and 10-12 tq gains from this tune alone?

What do you guys think about the option of this or the Prospeed tune(s) options that I have to choose from??

Thx

My understanding is the early chips (of which this is one) were hit or miss on performance improvements. The Dali chip was rumored to be a burned copy of the JDM NA1 NSX-R ECU map. The RM, Dinan, Autothority and G-Force chips actually lost power on some cars. I thought SOS stopped production because gains were not consistent, but I'm sure what Chris told you is probably better than the Prime rumor mill lol.

Also, be careful because the chip raises your rev limiter to 8,300. This puts you in range to grenade your oil pump gear.

I was thinking of getting my car re-mapped at MAC Autosport in Parker. It is always better to have a tune done to match your specific mods and preferences than an off-the-shelf kit. For example, I don't care about a dyno queen, but would like to see more torque under the curve in my typical driving range (2,000 to 5,000) to improve my daily driving experience. A custom tune can do that.

Cool thanks for the feedback on the chips you mentioned and specifically the SOS one. Looks like I'll either be getting the Prospeed stage 2 ecu rom tune or the RDX injectors and tune together?? Sounds like what your looking for "more torque under the curve (2,000 to 5,000)" is the RDX injectors and accompanying tune from Brian?

As you know, Greg, I had the original Prospeed stage 3 ecu for about a while. It made a noticeable difference, which like all things new, rapidly became the new normal. About a year later, I bought the RDX injector kit and sent the stage 3 chip back to be reprogramed. During the time the chip was in California, I replaced the factory chip so I could drive the car. The difference was permanently imprinted on my brain. The decrease in performance was marked and did NOT become the new normal -- thank goodness. Installing the RDX injectors provided an enormous boost in the mid range, 2000 - 5000 rpm. It was a whole new car.

Last summer I contacted Brian about his new high-altitude tune he made for a customer in Albuquerque
. As you may remember it has some issues in the cross-over to VTEC range, and we are working on them right now. I anticipate a solution sometime next month.

My take, FWIW, the Stage 2/3 chip is good and makes a noticeable difference. The RDX injector kit and chip makes a whole new driving experience.

Mark

Mark,

Thanks for the feedback, I do remember when I met you at the meet and greet last September (I think that's when it was) when we went for a drive in your car that the crossover to VTEC around 5800 was definitely noticeable, almost like it paused for a second before it hit VTEC range? Is that what your talking about? I haven't forgotten the power you gained in the upper range after VTEC though and it's been on my mind lately as to when I should get it, or if I should get high flow cats before I do the RDX upgrade?

"when we went for a drive in your car that the crossover to VTEC around 5800 was definitely noticeable, almost like it paused for a second before it hit VTEC range?"

That is exactly what I mean. I've contacted Brian privately and I have no doubt we will fix this RSH (Real Soon Now). I also am aware that he has changed the parameters since then, so we will see. What I hope for is the previous mid range torque back from the original tune, with the ferocious upper power with the latter, high altitude tune. All I want is everything! We'll see what we get.

High flow cats would be on the bottom of my list for upgrades -- I am still running my originals. The only benefit I could see would be full power and full rpm -- an area I don't spend all that amount of time at.

I don't remember if you have headers, but if not that is the very first thing to do on an NA1 engine. Getting rid of the '47 Buick cast iron headers not only gives between ~15 - 25 HP, it gets rid of about 30lbs.

When did he change the parameters of the tune? Was that when he said he released the Ver2.? Believe it or not I read through all 22 pages (550 posts worth) of the thread yesterday to refresh myself with the mod and what had been done since it's release in Feb '12'. I know he said that he combined the low altitude tune with the high altitude one he created when one of the Prime members from Albuquerque flew him out there to do a custom tune for the altitude. Do you have that particular tune where he said that he combined the two together? I think he talks about that a few pages before the end of the thread maybe around pg 18 - pg22?

And yes I have done the headers already, I don't think that I had them done when I had met with you at that car meet, but shortly afterwards I had the Pride headers installed. It was nice to get the cast iron boat anchors off as well! I have the old HKS sport exhaust on the car that came with it when I bought it, I don't know how free flowing the exhaust is though? It mimics the look of the stock exhaust and looks to be just as big, so I'm pondering getting the lightweight Pride exhaust to free up some flow possibly??

By the time you guys spend money on I/H/E, tuning etc etc you could be 1/3 of the way to a turbo system.
No owner is really ever happy with na mods. You can chase and extra 30hp but there is no replacement
for FI.
Ask anyone that has owned an NSX for a longer period and then gone sc or turbo, its like they have a new love
affair with the car. I gotta tell you, the group buy sc was a phenominal deal and has made a lot of owners faces
have a permenant grin.

Unfortunately I missed that group buy last year because I didn't have my car yet:frown: that might have been an option but that's neither here nor there. How much did you Angus Turbo system cost you? I can see by your RWHP and 1/4 mile time that it looks to have been worth it! Those look like great numbers for only 7.5 PSI!! Nice:biggrin:

Edit: I saw the price on his thread at about $6800! Ouch lol well for now I'll stay NA.... then down the road maybe forced induction?

FI versus NA is a never-ending discussion lol, and you're right- if dollars per horsepower is your goal for the NSX, the FI is the way to go. Some of us like to stay NA though. IMHO, it is closer to the spirit of Honda. I find my NSX is plenty fast at the track even without a supercharger.

As for the RDX mod, Mark is brave and is serving as a beta tester for Prospeed. With the current documented bugs, I can't put this system into my NSX, which is my daily driver that I rely on for transportation. I would go with the SOS chip first, but like I said a custom tune will yield better results.

The car feels pretty fast now as it is, but then again I've only had the car for about 7 months so my ownership experience is still pretty new. Regardless I'm still going to do HFC and possibly a better flowing exhaust system then what I have on there right now. Looks like I'm leaning towards the group buy that Mark is doing at Pride for their HFC, the price point is pretty good. Can you give me more info on that Super Ti exhaust system that you were mentioning in another thread??

Thx

MileHighNSX said:

The car feels pretty fast now as it is, but then again I've only had the car for about 7 months so my ownership experience is still pretty new. Regardless I'm still going to do HFC and possibly a better flowing exhaust system then what I have on there right now. Looks like I'm leaning towards the group buy that Mark is doing at Pride for their HFC, the price point is pretty good. Can you give me more info on that Super Ti exhaust system that you were mentioning in another thread??

Thx

Click to expand...

Save your money on the cats. They will not increase performance for your stock 3.0. HFC are really for guys with turbos and superchargers.

The Super Ti exhaust is, in my opinion, the ultimate NSX exhaust. It was designed by Fujitsubo specifically for the Japanese NSX owner, who was typically older and relatively wealthy. This customer wanted an exhaust that was polite and discreet while cruising around town, but would deliver maximum performance and sound at the track. This is not an easy task, since the NSX C30A has several resonant frequencies that must be addressed. Dave's (Mac Attack) research showed a serious resonance at 105 hz, which is much of the "drone" that we hear between 2,000 and 3,000 rpm. But, it is more complicated than that. A look inside the stock muffler gives us a clue.

http://www.nsxprime.com/forum/showthread.php/68558-Nsx-Muffler-Cutaway-and-Modify-Pics-Inside!

Trev did the NSX community a huge favor and provided the pics above. As you can see, the stock muffler is a very complex design. Seven chambers with multiple connections of differing lengths. The point of all these pipes and chambers is that they are a series of hemholtz resonators designed to attenuate the specific frequencies where the C30A makes a lot of noise. It is not easy to figure these frequencies out- you need experience and expensive software. The result is a muffler that is silent at idle, has no drone or boominess at 2,000 rpm, and is quiet up to 5,000 rpm where it gets a bit louder. It also weighs almost 50 lbs! If you read the entire thread, another owner cut some piping out "to make it sound better" and ended up with drone.

Instead, the right way to do it is to remove or reduce the baffles that attenuate the higher frequencies associated with 5,000+ rpm driving (this also increases flow), while preserving the baffles that attenuate the low frequency drone and idle noise (thus preserving backpressure and throttle response). Fujitsubo is one of the oldest exhaust companies in Japan and they have the resources and software to accomplish this difficult task. I strongly suspect they cut open a stock muffler, measured it, fed the data into their computer and worked off of that. When they were done, they had a stainless version that was perfect sound, increased about 7 whp, but it weighed almost as much as the stock muffler. So, they built the whole thing out of titanium and that is the Super Ti.

Specs are below. Pay attention to the decibel readings. This muffler is only slightly louder below 5,000 rpm and identical to the stock muffler at cruise speed, but above that range you can see how they opened up the flow. It is much louder at high rpm, like the Pride Lightweight or GTLW. And, the best part is it only weighs 20 lbs! That is why I think it is the best muffler you can buy for the NSX- it is a no-compromise solution. You get comfortable daily driving with no drone whatsoever, power increase, amazing howl at high speed, and you save 25 lbs of weight behind the rear axle. No US manufacturer has been able to replicate this, mostly because I think none of them want to spend the R&D dollars that Fujitsubo did to yield this result for such a small market. I really wish someone would because the $4,500 price is enough to make your eyes bleed. I do have some stock options vesting this year, so maybe I will treat myself if I can convince Mrs. Honcho, that is.

https://www.fujitsubo.co.jp/prods/detail/000000000000001341/00000000000000002989/00000118

Thanks for the detailed explanation of the exhaust! Sounds like an exotic exhaust system for the NSX, let me know if you end up getting that exhaust for your car I would love to hear it in person!!:biggrin:

The only reason I wanted to get the HFC was because when my car was in the air you can see coming from the Pride headers onto the cats it goes to a smaller diameter piping then out to the HKS sport exhaust which has a larger opening than the cats. I'm assuming the diameter of the HKS exhaust and the Pride headers are the same at around 2.25"? So I thought to myself that there is a choke point at the cats?? Maybe I'm wrong and that doesn't matter too much? What do you think?

Thx

MileHighNSX said:

The only reason I wanted to get the HFC was because when my car was in the air you can see coming from the Pride headers onto the cats it goes to a smaller diameter piping then out to the HKS sport exhaust which has a larger opening than the cats. I'm assuming the diameter of the HKS exhaust and the Pride headers are the same at around 2.25"? So I thought to myself that there is a choke point at the cats?? Maybe I'm wrong and that doesn't matter too much? What do you think?

Thx

Click to expand...

You are technically right- there is a "bottleneck" on the stock cats, since the diameter goes down. But, your engine does not flow enough CFM for it to matter, even with headers. If anything, that bottleneck is inducing a little bit of backpressure and making your throttle response off the line better. The Pride headers have an exit of 60mm, which is about 2.25". Not sure about the HKS, but that is a nice exhaust.

As for the Super Ti, looks like we might have a few owners who are interested in them. I'll let you know if I end up getting one.

Cool makes sense, What do you know about the HKS Sport exhaust that's on my car?? All I know is it was made to mimic the look of the stock exhaust system with the oval tips, but that's all I know? I think somebody said that it was one of the first aftermarket exhaust systems for the NSX available in the early nineties?? Don't know how true that is, but I would be interested in the specs of the exhaust, how much it cost when it was new, and what kind of gains were seen from this particular exhaust or if it was merely a better sounding exhaust system back in the day?

Thx

You are right- the HKS was one of the first exhausts available for the NSX in the 90's. It is Japan-designed and manufactured with immaculate build quality, including JASMA certification. It has been discontinued for some years, but the HKS was one of the "civilized" exhaust options back in the day, intended for owners who wanted a slightly more aggressive tone and extra power, but nothing over the top. It definitely flows better- HKS quoted about a 5 whp increase over the stock unit. It is fairly heavy though. Honestly, it is not worth changing from such a nice exhaust unless you want a different sound or are after weight savings. If you are after performance increase, then it is already doing that for you.

Thanks for that info! Sounds about right though, it looks just as heavy as the stock exhaust but with just bigger diameter piping. I can see the allure of going to a different/exotic sounding exhaust system, but if this is as well made as you explained then maybe I'll just keep it on the car after all? Shoot for all I know it's over 20 years old and it looks pretty good still for the age!

Boy this thread derailed from the original posting lol but I'm glad I got some information on the HFC and the exhaust system. Now back to what to do about that RDX tune or SOS tune?? I talked to Mark a couple of days
ago and he is still waiting for Brian to get a hold of him and figure out the VTEC change over issue that he is having with the tune itself. He said that before he went to the combined high altitude tune + regular RDX tune that it definitely had more get up and go in the mid-range and he wants that driveability back in that range, so we'll see what Brian cooks up for him and that'll give me an indication or not on which way I'm going to head with a tune.